The nation is presently faced with an energy shortage which is worsening at a rapid rate. Many people believe that the only way this condition can be relieved is to enlarge the use of coal and oil derived from rock shale with the corresponding reduction of the need for petroleum. There are known systems for mining coal and mineable materials which include the features of being multi-level and which convert the mined material into a slurry and pump the slurry to the ground surface. It is also known to derive power from a column of water which downflows from a surface reservoir to an underground reservoir and use the power to pump the slurry from a slurry mix tank through an upflow tube.
It is believed that none of these known mining systems are adapted to effect the efficiencies and economies that are required. Also, the application of retreat mining as disclosed herein will offer safety features with regard to personnel entrapped underground.